Biostimulants are chemicals that stimulate plant growth and increase plant protection from biotic and abiotic stress. Protein hydrolysates are classified as one type of biostimulant, and have been shown to have a positive effect on plant growth. The effect of gelatin, a kind of animal protein hydrolysate was evaluated on plant growth. Enhanced plant growth was measured in the aboveground portions of plants with the application of gelatin capsules applied at time of sowing adjacent to seeds. The crops tested (cucumber, tomato, broccoli, corn, arugula, pepper) showed increased plant growth as measured by leaf area, fresh and dry weight. The magnitude of plant growth enhancement was crop specific, and cucumber was used as the model crop for all further studies. Plants treated with gelatin capsules exhibited increased nitrogen content, and increased salinity tolerance compared to the non-treated control. Different types of hydrolyzed collagen, including granulated gelatin, gelatin hydrolysate, and amino acid mixtures containing amino acids present in gelatin were compared and revealed that granulated gelatin treatment had the greatest plant growth compared with other treatments. Plants were treated with two gelatin capsules and equivalent amounts of nitrogen in the form of urea, revealed that increased plant growth from the application of gelatin capsule was not solely due to the nitrogen. RNA-seq results provided some insights on the mechanisms of the growth promotion from the gelatin capsule treatments. Genes were upregulated from the gelatin treatment involved in nitrogen transport including ammonium transporters and amino acid transporters, and MYB and WRKY family transcription factors that regulate diverse pathways including abiotic stress tolerance and other responses were upregulated in plants with gelatin treatment. Genes involved in detoxification such as Glutathione S-transferase exhibited a high positive correlation with increase leaf area and nitrogen content in plants treated with gelatin capsule.